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Unformatted text preview: And this just feels like spinning plates My body is Foating down the muddy river (Radiohead) Looking forwards Next, we will discuss features of protein function-Protein binding: how proteins interact with other molecules and other proteins to enable function Example: transport of oxygen by hemoglobin-Enzymes: Proteins as reaction catalysts (cooperativity)-Enzyme kinetics-Enzyme regulation Today: 1) Protein binding and the dissociation constant (K d ) I have posted answers to your questions (e-mails) on Blackboard under Questions The PyMol program, a tutorial, and the Builds that I showed in class are in the Course materials section on Blackboard 2) Myoglobin and oxygen binding 3) Hemoglobin 4) Enzymes and catalysis Note: reading for most of this lecture is pp. 153-170 In Lehninger, Principles of Biochemistry, 5th ed. a pdf is posted on Bb!!-Structure-Cooperativity-pH and CO 2 transport (the Bohr effect))-BPG and avoiding altitude sickness Summary 1) A dissociation constant (K d ) provides useful information about the affinity between ligands and proteins 2) Hemoglobin has two conformational states. Switching between them facilitates efficient O 2 binding in the lungs and release in capillaries. 4) Hemoglobin exhibits allostery in several reactions. Linking of the conformational transitions of the subunits through allostery leads to cooperative O 2 binding and release 5) BPG inhibits O 2 binding (to T state), enabling regulation of O 2 affinity in response to the environment. 3) The local environment can shift pKa values significantly. A pKa shift of specific histones in Hb drives proton and CO 2-binding and release in inverse to O 2 binding. The problem: http://www.freerepublic.com/focus/f-bloggers/2780879/posts O 2 diffuses through tissue up to about 1 mm At a rate sufficient to support life Fine for yeast Not so much for humans O 2 is soluble in blood plasma to about 10-4 M (100 M) http://www.darkexistence.com/ Fine for vampires A solution: Whole blood contains about 150 g/L hemoglobin...
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